Fixing compatibility with Rails 7 and API mode

app/controllers/devise_controller.rb

@@ -3,6 +3,7 @@
 # All Devise controllers are inherited from here.
 class DeviseController < Devise.parent_controller.constantize
   include Devise::Controllers::ScopedViews
+  include Devise::Controllers::Rails7ApiMode
 
   if respond_to?(:helper)
     helper DeviseHelper

lib/devise.rb

@@ -22,6 +22,7 @@ module Devise
 
   module Controllers
     autoload :Helpers,        'devise/controllers/helpers'
+    autoload :Rails7ApiMode,  'devise/controllers/rails7_api_mode'
     autoload :Rememberable,   'devise/controllers/rememberable'
     autoload :ScopedViews,    'devise/controllers/scoped_views'
     autoload :SignInOut,      'devise/controllers/sign_in_out'

lib/devise/controllers/rails7_api_mode.rb

@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+module Devise
+  module Controllers
+    module Rails7ApiMode
+      extend ActiveSupport::Concern
+
+      class FakeRackSession < Hash
+        def enabled?
+          false
+        end
+      end
+
+      included do
+        before_action :set_fake_rack_session_for_devise
+
+        private
+
+        def set_fake_rack_session_for_devise
+          if Rails.configuration.respond_to?(:api_only) && Rails.configuration.api_only
+            request.env['rack.session'] ||= FakeRackSession.new
+          end
+        end
+      end
+    end
+  end
+end

test/controllers/rails7_api_mode_test.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class Rails7ApiModeTest < Devise::ControllerTestCase
+  tests Devise::SessionsController
+  include Devise::Test::ControllerHelpers
+
+  test 'is injected into the Devise controllers' do
+    assert @controller.is_a?(Devise::Controllers::Rails7ApiMode)
+  end
+
+  # note: disabling API mode in one test seems not feasible; the test harness breaks a little bit.
+  #       we need to understand better how to cover API-only mode in devise to prevent future issues.
+end